In various contexts it is necessary to remove coatings such as adhesives, paint and thermal spray coatings from an underlying surface, for example, jet engine components. Such coatings are difficult to remove, particularly thermal spray coatings which are exposed to high temperatures during service. Such coatings are typically used on burner cans, combustion chambers, stator and rotor blades, and other parts of a jet engine that are exposed to an extremely harsh environment.
After an engine has been in service for a given number of hours, areas of the coating will begin to weaken and deteriorate, due to being exposed to high temperatures and stresses. Because the jet engine parts are typically very costly, it is desirable to replace a weakened coating rather than replace the engine part. Given the high quality coating that needs to be achieved, it is unacceptable to simply recoat a part. It is also necessary to remove an old coating so that the substrate may be examined for wear and fatigue and repaired if necessary, after which the part may be recoated.
In the past, such hard coating removal has been accomplished by using extremely aggressive and toxic chemicals. Given environmental concerns, this method is becoming more and more unacceptable. Hard coating removal is also currently achieved by machining and grinding. However, aircraft and jet engine parts typically do not have a standard shape, given that components such as burner cans and combustion chambers are made of sheet metal and are therefore easily warped with usage. As a result, it is very difficult to set up machining for the removal of hard coating through grinding, and such a process is virtually impossible to automate. Although parts may be ground by hand, such a process is time consuming and slow, and is believed to potentially expose an operator to toxic dust.
A need therefore exists for an improved method of removing hard coatings from underlying surfaces.